CD19 is a hallmark of B-cells since CD19 is expressed on the surface of human B cells including pre-B cells, immature B cells, mature B cells and malignant B cells. CD19 has been used to diagnose cancers that arise from B cell (e.g., B-cell lymphomas). Further, some drugs associated with anti-CD19 may direct treatment specifically towards B-cell cancers. For example, CD19 monoclonal antibody may be used for the treatment of B-cell related diseases.
Monoclonal antibodies are typically made entirely from mouse cells. One problem with this is that the human immune system may see these antibodies as foreign and may mount a response against them. In the short term, this can sometimes cause an immune response. In the long term, this may cause the antibodies to only work the first time(s) they are given. After the first time, the human immune system may destroy these antibodies before the desired treatment takes place.